Can a federal guilty drug charge brought against an active duty member of the military be removed from a criminal record?

While serving active duty in the Marines, I was found guilty of illegal possession of a controlled substance but my urine was clean and I had no drugs or paraphernalia in my possession. The guilty charge stems from a confession I made stating I had smoke marijuana after being interrogated and under investigation by the Naval Criminal Investigative Service who had our whole unit under surveillance. I was told that if I didn't cooperate I would go to the brig so I cooperated by confessing and went to Iraq instead. Now a federal drug charge pops up every time someone runs a background check on me. I'm not sure if it reads as a felony but no one has let me look at my own records and employers want disposition papers that I don't have so I'm not sure what to do except try and figure how to get this thing off my record, so I can get a job.